Imine Directed Cp*RhIII -Catalyzed N-H Functionalization and Annulation with Amino Amides, Aldehydes, and Diazo Compounds.

A multicomponent annulation that proceeds by imine directed Cp*RhIII -catalyzed N-H functionalization is disclosed. The transformation affords piperazinones displaying a range of functionality and is the first example of transition metal-catalyzed multicomponent N-H functionalization. A broad range of readily available α-amino amides, including those derived from glycine, α-substituted, and α,α-disubstituted amino acids, were effective inputs and enabled the incorporation of a variety of amino acid side chains with minimal racemization. Branched and unbranched alkyl aldehydes and various stabilized diazo compounds were also efficient reactants. The piperazinone products were further modified through efficient transformations. Mechanistic studies, including X-ray crystallographic characterization of a catalytically competent five-membered rhodacycle with imine and amide nitrogen chelation, provide support for the proposed mechanism.

Copper-Catalyzed Three-Component Synthesis of Highly Substituted Morpholines.

Unprotected, highly substituted morpholines were obtained through a copper-catalyzed three-component reaction utilizing amino alcohols, aldehydes, and diazomalonates. The transformation was effective for diversely substituted aldehydes and for a broad range of readily available vicinal amino alcohols, including those derived from glycine, α-substituted, and α,α-disubstituted amino acids. Epimerization of morpholines using light-mediated stereochemical editing was demonstrated, and the unprotected morpholine products were readily elaborated through efficient transformations.

Annulation of Hydrazones and Alkynes via Rhodium(III)-Catalyzed Dual C-H Activation: Synthesis of Pyrrolopyridazines and Azolopyridazines.

Hydrazones readily synthesized from N-aminopyrroles or N-aminoazoles and aldehydes undergo Rh(III)-catalyzed dual C-H activation and coupling with aryl- and alkyl-substituted alkynes to give pyrrolopyridazines or azolopyridazines, respectively. This transformation represents a rare example of hydrazoyl C-H activation and proceeds without heteroatom functionality to direct C-H activation. Hydrazones derived from aromatic, alkenyl, and aliphatic aldehydes were effective inputs, and tethering the alkyne to the hydrazone enabled annulations to more complex, tricyclic products.

Three-Component Coupling of Aldehydes, 2-Aminopyridines, and Diazo Esters via Rhodium(III)-Catalyzed Imidoyl C-H Activation: Synthesis of Pyrido[1,2- a]pyrimidin-4-ones.

Imines formed in situ from 2-aminopyridines and aldehydes undergo Rh(III)-catalyzed imidoyl C-H activation and coupling with diazo esters to give pyrido[1,2- a]pyrimidin-4-ones. Aromatic and enolizable aliphatic aldehydes were both effective substrates, and a broad range of functional groups were incorporated at different sites on the heterocyclic products. In addition, methoxy and dimethylamino functionalities could be directly installed on the pyrimidine ring by employing trimethyl orthoformate or N, N-dimethylformamide dimethyl acetal in place of the aldehyde, respectively.